Background to Michell Instruments

Michell Instruments is the international leader in the field of moisture and humidity measurement solutions. With over 30 years experience, Michell designs and manufactures a wide range of transmitters, instruments and system solutions capable of measuring trace moisture, humidity and dew point in a vast range of applications and industries ranging from compressed air, power generation, process, oil and gas, pharmaceutical and many more.

With a fast growing international subsidiary and distribution network, the Michell Group provides solutions in moisture and humidity for the most demanding applications worldwide. Michell uses five primary moisture measurement technologies across the product line:

Impedance - using a patented ceramic tile that delivers unrivaled speed of response, stability and ruggedness

Sensor Technology

Ceramic Impedance Sensor
Michell Instruments’ portable dew-point meters use the Advanced Ceramic Moisture Sensor. The operation of this sensor depends on the dielectric property of water molecules absorbing onto an active porous insulating layer sandwiched between two layers of conductive material deposited on a ceramic substrate. Water has a very high dielectric compared to the dielectric of the active layer and the background of the carrier gas so it can be detected easily. The active layer is very thin – less than one micron and the porous top conductor that allows water molecules to penetrate into the active layer is less than 0.1 micron thick. This allows the sensor to respond very rapidly to changes in the moisture surrounding it both when moisture decreases (drying) and increases in the sensor environment.

Capacitive Humidity Sensor

A capacitive humidity sensor works like a classic plate capacitor. The lower electrode is deposited upon a carrier substrate. A thin polymer layer acts as a dielectric. The upper capacitor plate is configured as an electrode which is transmissive to water vapour. The polymer layer is hygroscopic. Water molecules enter this layer and alter its dielectric constant and this results in the changing of the capacitance that can be measured and processed by electronics.